Displays such as cathode-ray tube (CRT) displays, liquid crystal displays (LCDs), plasma display panels (PDPs), and electroluminescence (EL) displays are required to have various functions of preventing scratch damages, preventing reflection of images, and preventing fouling, on their surfaces.
Thus, the surface of a common display is provided with a protecting plate or an optical filter having functions such as an anti-reflection property, antiglare property, hard coating property, antistatic property, anti-fouling property, gas barrier property, and UV (ultraviolet rays) shielding property (see Patent Document 1, for example). Patent Document 1 discloses an optical filter comprising a near infrared radiation reflective layer including a transparent high-refractive-index thin-film layer and a metal thin-film layer for the purpose of shielding near infrared rays and electromagnetic waves radiated from the screens of displays such as plasma display panels, and an optical filter further comprising a commercially available anti-reflection film laminated thereon and thereby being imparted with anti-reflection and anti-glare properties.
Examples of common anti-reflection films include AR (anti-reflection) films and LR (low reflection) films in which the surface of a substrate is covered with a film having a refractive index different from that of the substrate, and reflection is reduced owing to the interference effect between light reflected from the substrate surface and light reflected from the surface of the applied film. Further, examples of common anti-glare films include AG (anti-glare) films in which the substrate surface is covered with a film having a fine uneven pattern, and thus reflection of images is prevented owing to the light scattering effect.
Such an anti-reflection film, however, has a high absolute value of the reflectance and strong wavelength dependence, and thus reflection of the surroundings and coloring due to reflected light occur. Therefore, the film can be further improved in these respects.
In contrast, a moth-eye structure is being focused on as a technique for improving visibility at bright sites different from the above films. The moth-eye structure can provide an ultra-anti-reflection effect without light interference. The moth-eye structure is a structure that a fine uneven pattern at a pitch of not greater than the visible light wavelength (for example, 400 nm or lower), which is finer than the uneven pattern formed on an AG film, is arranged without any gap on the surface of an article to be anti-reflection-treated, and thereby the refractive index at the boundary between the outside (air) and the article surface pseudo-continuously changes. Thereby, most part of light is transmitted regardless of the refractive index interface, and light reflection from the article surface can be almost perfectly prevented (see Patent Document 2, for example).
Patent Document 1: JP 2002-323860 A
Patent Document 2: JP 2004-205990 A